Review of a systematic approach for suspected difficult intubation under general anaesthesia
Bibliographic record
Abstract
We routinely use the Glidescope (GS) in patients with suspected difficult airways. However, failure to use a standard Macintosh (Mac) blade prevents confirmation of difficult laryngoscopy and causes probable overuse of an expensive videolaryngoscope. Since the McCoy blade has a Mac profile in the neutral position, by first using the McCoy, one can confirm the clinical suspicion and if necessary trial the alternative blade profile, all during a single direct laryngoscopy. Our aims were to provide vital airway information that is missed if only the GS is used, to reduce the use of the GS where not needed, and to compare McCoy and GS laryngoscopic views. After ethics approval, we audited a systematic approach to difficult intubation using the McCoy blade, followed by the GS if the initial Mac and McCoy views were inadequate. Data were analysed from an anonymous quality assurance form on which airway characteristics and laryngoscopic grades had been recorded by the attending anaesthesiologist. A laryngeal grade ≥ 3 was considered to be difficult. In 61 patients predicted to have a difficult intubation, the Mac view confirmed the clinical suspicion in 42 (69%), of which there were four cases of grade 4 and 38 cases of grade 3 views. The McCoy converted 4/4 Mac grade 4 views to grade 3 and 27/38 (70%) Mac grade 3 views to grade < 3. The GS converted all of the residual McCoy grade 3 views (4 + 11) to intubatable views. There were no failed or fibreoptic intubations. In 34 patients, the anaesthetist decided to complete all three laryngoscope views. The Mac view was difficult (grade ≥ 3) in 28 (82%), the McCoy view was difficult in 14 (41%) and the GS view was difficult in none (see Table). Analysis using McNemar chi-squared test showed the difference between McCoy and GS views to be highly significant. By first achieving a Mac view, 19/61 (31%) of suspected difficult intubations were found to be intubatable. The McCoy blade is a simple portable device that successfully changed a difficult grade 3 view into a manageable one in 70% of cases. However, the GS appears to be a superior tool in that it converted 29/29 (100%) of grade 3 and 4 Mac views into intubatable views. It must be remembered that a good GS view does not necessarily mean an easy intubation. Costs aside, we must be careful not to overuse our videolaryngoscopes as this could lead to a skill fade in direct laryngoscopy. We feel that videolaryngoscopy should be emphasised in the DAS guidelines. A randomised controlled trial is required to confirm these promising results. Using a systematic approach to suspected difficult intubation under GA, we found the McCoy blade to be valuable. The Glidescope however gave far superior laryngoscopic exposure converting all grade 3 and 4 Macintosh views into intubatable views.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.026 | 0.176 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.006 | 0.005 |
| Bibliometrics | 0.036 | 0.022 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".